菌根诱导的CySWEET14调控大花蕙兰与印度梨形孢共生关系的分子机制

The green orchids establish mutualism with their mycorrhizal fungi, and the essential basis of the mutualism is sugar transport, including sucrose. The plant sugar transporters are responsible for the sugar efflux. But none of key sugar transporters has been identified to regulate mycorrhizal symbiosis. Therefore, it is of great scientific significance to carry out the research on the function of newly identified sugar efflux transporters-- SWEETs in mycorrhizae. Based on our previous work, this program will focus on the mechanism that how CySWEET14 and mycorrhizal fungi effectors co-operate to regulate plant mycorrhizal symbiosis using the symbiotic system between Cymbidium hybridum (or Arabidopsis thaliana)--- Piriformospora indica. The main works include: analysis of the sugar efflux characteristic of CySWEET14 and its mycorrhizal- induced expression pattern; the identification of fungal effectors (CAEs) interacting with pCySWEET14; the physiological activity of CAEs in mycorrhizae; the physiological and biochemical evidences of CySWEET14 being regulated by CAEs in the symbiotic process, and so on. It is our goal to exemplify the importance of the sugar efflux function of CySWEET14 for the mycorrhizal symbiosis, to obtain the direct evidence of fungal effectors (CAEs) interacting with pCySWEET14, and to construct the model how the SWEETs members regulate the symbiosis between plant and beneficial microorganism, so as to establish the foundation for regulating mycorrhizal relationship.

绿色兰科植物在成株期与菌根真菌之间形成互惠共生体，其互惠的根本基础是包括蔗糖在内的糖分转移。糖转运蛋白负责将植物糖分外运给菌根真菌，但迄今还未发现调控菌根共生的关键性糖转运蛋白。所以，糖转运蛋白SWEETs在菌根中的功能研究具有重要科学意义。基于前期研究结果，本项目以大花蕙兰(或拟南芥)--印度梨形孢共生体系为研究对象，重点研究CySWEET14与菌根菌效应因子如何协同工作调控植物菌根共生。主要研究内容包括：CySWEET14的转运活性和表达特性；与pCySWEET14 互作的真菌效应因子CAEs鉴定; CAEs在菌根中的生理活性；CySWEET14受CAEs操纵表达调控菌根共生的生理生化证据等。试图阐释CySWEET14 的糖外运功能作用于菌根共生的分子机制，获得共生菌效应因子操纵宿主糖转运蛋白表达的直接证据，构建SWEETs成员调控菌根互作的工作模型，从而为调控菌根共生关系奠定理论基础

绿色兰科植物成株与菌根菌（OMF）之间存在互惠共生关系。本项目从CySWEET14糖外运功能的验证以及兰花菌根形成中的重要真菌效应因子鉴定等方面获得了丰富、科学的数据，从而可以初步构建SWEETs成员调控植物与有益微生物互作的工作模型。本项目实施将为解析菌根共生关系提出新的思路，从而为拓宽菌根真菌的宿主范围或者提高菌根效应提供新的分子依据。取得的主要研究结果如下：（1）获得印度梨形孢与拟南芥、大花蕙兰均可形成良好共生关系的LW01c培养基；（2）利用拟南芥atsweet11;12突变株和CySWEET14异源超表达验证CySWEET14具有蔗糖转运功能；（3）CySWEET14的拟南芥同源基因（AtSWEET11-14）在拟南芥与印度梨形孢共生过程中扮演的角色与CySWEET14在OM菌根形成中发挥的功能不同：AtSWEET11和AtSWEET12负调控内生菌共生过程；（4）CySWEET14启动子长度大于353bp时可以成功在拟南芥中表达，但其表达并不具有真菌特异诱导的特性；（5）印度梨形孢效应因子（PIIN_01386、PIIN_01928、PIIN_06901、PIIN_07212、PIIN_08228 和PIIN_10699）在兰花菌根形成中扮演重要角色。